1. Field of the invention
The present invention relates to a film winding/rewinding mechanism of a camera using an ultrasonic wave motor.
2. Description of the related art
A film winding/rewinding mechanism of a camera using an ultrasonic wave motor as the driving source has been proposed. For example, Japanese Patent Laid-Open Publication No. 2-29724 discloses a film winding/rewinding mechanism using progressive wave type ultrasonic wave motors, one of which drives the winding side and the other of which drives the film rewinding side. In this winding/rewinding mechanism, the driving side causes a vibrator to generate progressive waves on the surface thereof so as to impart a predetermined rotational force to a rotor, i.e. a film winding spool, while the driven side causes a vibrator to generate standing waves so as to reduce the resistance to the rotor.
Japanese Patent Laid-Open Publication No. 63-77039 discloses a winding/rewinding mechanism in which a clutch is used to adjust the resistance to the rotor of the driven side.
According to the winding/rewinding mechanism disclosed in Japanese Patent Laid-Open Publication No. 2-29724, both the film winding driving section and film rewinding driving section are provided with a circuit for generating standing waves in addition to a circuit for generating progressive waves. That is, in both the film winding and film rewinding operations, progressive waves are generated by the driving side and standing waves are generated by the driven side. Since it is necessary to operate two circuits simultaneously, the mechanism has a high consumption of power.
According to the winding/rewinding mechanism disclosed in Japanese Patent Laid-Open Publication No. 63-77039, the clutch is used to reduce the force for holding the rotor of the driven side. Therefore, the winding/rewinding mechanism requires a great space.